Process for microwave-driven catalytic reforming of polyolefin cracking

Abstract

The present application relates to the field of oil and gaseous hydrocarbon preparation by microwave-driven polyolefin pyrolysis reforming. More particularly, it relates to a process method of microwave-driven catalytic polyolefin pyrolysis reforming. The polyolefin pyrolysis reforming is carried out by using a microwave reaction device with a PLC control unit, a carrier gas adjusting unit and a reaction unit; the polyolefin raw material is located at the bottom of the reaction unit, the catalyst is stacked on the polyolefin raw material to form a catalyst bed, and the bottom of the catalyst bed is in contact with the polyolefin raw material to form a horizontal material contact surface; the process method comprises: under the action of microwave, the polyolefin raw material undergoes a pyrolysis reaction at the material contact surface to generate primary pyrolysis products; as the polyolefin raw material is consumed, the catalyst sinks under gravity and maintains the horizontal material contact surface; the primary pyrolysis products pass through the catalyst bed from bottom to top and are gradually pyrolyzed into oil components and / or gaseous hydrocarbon components, thereby realizing the catalytic reforming of the polyolefin raw material.

Description

Technical Field

[0001] This invention relates to the field of preparing petroleum products and gaseous hydrocarbons using microwave-driven polyolefin cracking and reforming. More specifically, it relates to a process method for microwave-driven catalytic polyolefin cracking and reforming. Background Technology

[0002] As a crucial material related to national economy and people's livelihood, the production of polyolefin plastics has been continuously increasing in recent years, leading to increased greenhouse gas emissions, primarily carbon dioxide, and the generation of waste polyolefin plastics, causing serious ecological pollution and resource waste. Traditional landfill and incineration methods are no longer suitable for the treatment of waste polyolefin plastics. Therefore, researchers are exploring how to chemically recycle waste polyolefin plastics to obtain gaseous fuels, hydrocarbon chemicals, and other chemical raw materials.

[0003] Polyolefin plastics, as solid polymers with high molecular weight and high bond energy C-C bonds, are difficult to biodegrade. In traditional pyrolysis, the plastic can decompose to produce hydrogen and hydrocarbons, but the molten plastic and post-reaction residues adhere to the reactor surface, limiting continuous feeding and reducing reaction efficiency. Even with the addition of a catalytic system to effectively improve product selectivity and increase product added value, the residues generated after catalytic cracking and reforming of polyolefin plastics often passivate active sites, blocking reaction sites that should be in contact with the material. This leads to a significant reduction in the lifetime of catalysts, especially solid acid catalysts with good activity and selectivity. Therefore, new technologies are needed to address these problems. Microwave-driven pyrolysis, as a novel pyrolysis technology that has emerged in recent years, offers high controllability, increases heating rate and heat transfer efficiency, and reduces energy consumption.

[0004] Therefore, to maximize the utilization of waste polyolefin plastics and address the problems of high energy consumption, low efficiency, easy catalyst deactivation, and insufficient process flexibility inherent in traditional thermochemical recycling, a microwave reaction device is introduced. This device features a layered design (especially with the catalyst and reactants contacting each other in a layered manner instead of the conventional uniform mixing contact scheme), optimizing the microwave-driven pyrolysis plastic reforming process and related technologies. Achieving high-value products from polyolefin plastics through microwave-driven catalytic pyrolysis helps alleviate climate change and global warming, promotes waste recycling, and achieves the goal of green and sustainable development. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a microwave-driven catalytic cracking and reforming process for polyolefins. This process cleverly stacks polyolefin feedstock and catalyst. The polyolefin feedstock in the lower layer reacts first at the material contact surface under microwave action. The resulting primary cracking products are continuously passed through the catalyst bed from bottom to top by the catalyst at the material contact surface, undergoing a step-by-step reaction to achieve cracking and reforming. The entire process has advantages such as controllable reaction and high reaction efficiency, realizing high-value-added conversion of waste plastics and generating higher economic value.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention discloses a microwave-driven catalytic polyolefin cracking and reforming process, which uses a microwave reaction device with a PLC control unit, a carrier gas regulation unit, and a reaction unit to perform polyolefin cracking and reforming. The polyolefin feedstock is located at the bottom of the reaction unit, and the catalyst is stacked on it to form a catalyst bed. The bottom of the catalyst bed is in contact with the polyolefin feedstock to form a horizontal material contact surface. The process includes: Under microwave irradiation, polyolefin raw materials undergo a pyrolysis reaction at the material contact surface, generating primary pyrolysis products; As the polyolefin feedstock is consumed, the catalyst sinks under gravity and maintains the horizontal material contact surface; The primary cracking products pass through the catalyst bed from bottom to top, and are pyrolyzed stepwise into oil components and / or gaseous hydrocarbon components, thereby achieving catalytic reforming of polyolefin feedstocks.

[0007] In microwave catalytic reforming, the catalyst and polyolefin feedstock are packed in an inner reaction tube, while the microwave-absorbing medium is placed in an outer reaction tube. During loading, the catalyst and the reactants to be decomposed are layered. By rationally controlling the reaction conditions, the polyolefin feedstock can be progressively decomposed within the catalyst bed, thus achieving the catalytic reforming process. Technicians can control the reaction path by changing the catalyst dosage or adjusting the height of the catalyst bed, making the feedstock conversion more selective. The entire process is economical and environmentally friendly, simple and flexible, low-cost, and the reaction is flexible and controllable. It exhibits high selectivity for olefin feedstocks, overcoming problems such as low product added value, low product controllability, easy catalyst deactivation, low safety factor, and high energy loss in the preparation of hydrocarbon chemicals and gaseous fuels. It has certain market application value and advantages.

[0008] In this invention, polyolefin feedstock and catalyst are stacked to form a reactant layer and a catalyst layer of a certain bed height, respectively. It should be noted that the reactant layer and catalyst layer should not be separated by other materials or partitions, allowing them to naturally form clearly defined material contact surfaces. Furthermore, to ensure consistent reaction progress along the same axis, the interior of both the reactant layer and catalyst layer should be filled as uniformly as possible, reducing unnecessary voids. The material contact surfaces should also be kept as flat as possible. Of course, if the materials are stacked uniformly before the reaction, the material contact surfaces will remain horizontal during the reaction process, thus ensuring consistent reaction progress along the same axis.

[0009] Furthermore, this invention utilizes the adjustment of microwave power to alter the real-time temperature of the reaction system. It's important to note that the reaction temperature controlled by this invention does not directly and completely pyrolyze the polyolefin raw materials. Instead, catalysis occurs at a relatively lower temperature, initiating the catalytic process at the material contact surface through the contact between the catalyst and the reactants, and then progressively achieving the pyrolysis process. In one specific embodiment, the pyrolysis reaction temperature is 200-550°C, and the pyrolysis reaction time is 10-60 minutes. Throughout the reaction, the polyolefin raw materials are continuously consumed. This will inevitably lead to the continuous depletion of the reactant layer. Because the catalyst bed and the reactant layer are in contact, the catalyst bed continuously sinks under gravity to maintain the contact surface between the reactant layer and the catalyst bed, ultimately until the polyolefin raw materials are completely consumed.

[0010] Furthermore, the mass ratio of the polyolefin raw material to the catalyst is 1:0.4-2.5; exemplaryly, the mass ratio of the polyolefin raw material to the catalyst can be 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, etc.

[0011] Furthermore, since neither the reactant layer nor the catalyst layer contains any substances that can absorb microwave energy, a microwave absorber is placed in contact with the periphery of the reaction unit to provide energy to the reaction unit by utilizing the microwave absorption capability of the microwave absorber.

[0012] Furthermore, the total mass ratio of the polyolefin raw material and catalyst to the microwave absorber is 1:0.1-10; for example, the total mass ratio of the polyolefin raw material and catalyst to the microwave absorber can be 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.

[0013] Furthermore, the height of the catalyst stacked bed is 30-60 mm; the height of the microwave absorber stacked bed is greater than the total height of the polyolefin raw material and the catalyst stacked bed, so as to ensure that the entire reaction process is under microwave influence.

[0014] Furthermore, the polyolefin raw material is selected from waste plastics such as polyethylene (PE) plastic, polypropylene (PP) plastic, and polystyrene (PS) plastic, as well as one or more biomass such as cellulose, hemicellulose, lignin, glucose, and starch.

[0015] Furthermore, the catalyst is selected from one or more of the following: molecular sieves without or with metal elements: carbon fiber, graphite, graphene oxide, reduced graphene oxide, carbon nanotubes, biochar, calcium oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, zinc oxide, and manganese oxide.

[0016] Furthermore, the microwave absorber is selected from one or more of unloaded silicon carbide, carbon fiber, graphite, graphene oxide, reduced graphene oxide, carbon nanotubes, biochar, iron oxide, cobalt oxide, nickel oxide, zinc oxide, and manganese oxide.

[0017] Furthermore, the metallic element is selected from one or more of zirconium, nickel, tungsten, zinc, iron, cobalt, copper, molybdenum, platinum, palladium, silver, and gold.

[0018] Furthermore, the biochar is derived from the pyrolysis products of rice husks, coconut shells, bamboo, corn cobs, corn stalks, wheat stalks, rice stalks, or rapeseed stalks.

[0019] Furthermore, the microwave reaction device also includes an automatic protection unit, which, through the linkage mechanism between the automatic protection unit and the PLC control unit, enables real-time online control of the input power of the microwave reaction device.

[0020] Furthermore, the linkage mechanism utilizes a PLC control unit to monitor the input power, reaction unit temperature, and reflected power in real time. When the reaction unit temperature reaches 200-550℃, the system automatically reduces the input power and maintains the reaction temperature. When the set reaction time is reached, the system automatically stops microwave heating. When the reflected power exceeds 50% of the input power, the protection unit is automatically activated to stop the microwave generator from working.

[0021] Furthermore, the microwave generator of the microwave reaction device is a magnetron or a solid-state source, operating in single-mode or multi-mode mode, with an operating frequency of 2.45 GHz or 915 MHz; The input power of the microwave reaction device is 0-8000 W.

[0022] Furthermore, an air inlet and an air outlet are respectively provided on the top of the reaction unit, and the air inlet and air outlet do not interfere with each other.

[0023] Furthermore, the carrier gas regulating unit supplies carrier gas to the reaction unit through the gas outlet. Supplying carrier gas before the reaction maintains a stable gas environment within the device, while continuing to supply carrier gas during the reaction allows the reaction products to flow out of the reaction unit under the entrainment of the carrier gas and enter the detection device.

[0024] Furthermore, the carrier gas is selected from one or more of argon, nitrogen, and helium, and the carrier gas flow rate ranges from 20 to 250 mL / min.

[0025] Furthermore, the microwave reaction device is also equipped with... Temperature monitoring unit is used to measure the real-time temperature of polyolefin raw materials and catalysts; A power detection unit is used to measure the input power and reflected power of the microwave reaction device; The cold trap liquefaction unit is used to reduce the temperature inside the microwave reaction device and to achieve the liquefaction and collection of reaction products.

[0026] Furthermore, the gaseous hydrocarbon component is selected from one or more of hydrogen, low-carbon hydrocarbons, and carbon monoxide; The oil components are selected from gasoline and diesel components mainly composed of benzene series compounds, and are obtained by liquefying the reaction products using a cold trap liquefaction unit; for example, they can be aromatics, olefins, alkanes, etc.

[0027] Furthermore, the temperature monitoring unit is located inside the microwave reaction device and includes an infrared temperature measuring device and a fiber optic temperature measuring device; the infrared temperature measuring device and the fiber optic temperature measuring device are respectively installed in the radial and axial directions, and the infrared temperature measuring device is arranged at multiple different heights in the radial direction according to the thickness of the material.

[0028] Furthermore, the power detection unit includes an input power detection unit and a reflected power detection unit.

[0029] Furthermore, the PLC control unit is connected to the temperature monitoring unit, power detection unit, cold trap liquefaction unit, automatic protection unit, microwave generator, and carrier gas regulating unit via circuitry to achieve real-time monitoring of the reaction unit's temperature, input power, reflected power, and weight, as well as control of the automatic protection unit.

[0030] The beneficial effects of this invention are as follows: The microwave-driven catalytic reforming process for waste polyolefin plastics described in this invention achieves efficient conversion of waste plastics into light olefins and aromatics by adjusting microwave power. The process features complete product collection, strong controllability, flexible operation, the ability to be terminated at any time, and high safety.

[0031] The microwave-driven catalytic reforming process for waste polyolefin plastics described in this invention has low energy consumption, fast heating speed, and the microwave absorbing medium and catalyst can be recycled multiple times, making it highly applicable and economically valuable.

[0032] The reaction tube and microwave reaction device of this invention, which are filled with layered materials, are all detachable and separable. The mass ratio and mixing scheme of the catalyst, waste plastics and graphite located in the reaction tube can be adjusted to control the reaction path, making the raw material conversion more selective. It can achieve the pyrolysis of raw materials and the secondary and multi-stage reforming of intermediate products under milder conditions, and better promote the efficient recycling and application of waste plastics and green sustainable development.

[0033] The microwave-driven catalytic reforming process for preparing oil products and gaseous fuels described in this invention produces oil products composed of one or more combinations of aromatics, olefins, and alkanes, and gaseous fuel components including one or more combinations of methane, hydrogen, and carbon monoxide. The oil products can selectively yield important BTEX basic chemical products (benzene, toluene, ethylbenzene, and xylene) by adjusting the process parameters of this invention, and the gaseous fuels can also selectively yield important chemical products such as hydrogen, ethylene, and propylene. This enables high-value-added applications of waste plastics and plays a positive role in solving the pollution and energy supply problems associated with waste plastics. Attached Figure Description

[0034] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0035] Figure 1 This is a design diagram of the microwave catalytic reforming process in Example 1 of the present invention.

[0036] Figure 2 This is the gas chromatography spectrum of Embodiment 8 of the present invention. Detailed Implementation

[0037] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0038] This invention uses commercially available microwave reaction equipment to conduct the following experiments. The microwave catalytic reforming process design diagram is shown below. Figure 1As shown, the microwave reaction device includes a PLC control unit, an automatic protection unit, a carrier gas regulating unit, a reaction unit, a temperature monitoring unit, a power detection unit, a cold trap liquefaction unit, and a microwave generator. The PLC control unit is connected to the temperature monitoring unit, the power detection unit, the cold trap liquefaction unit, the automatic protection unit, the microwave generator, and the carrier gas regulating unit through circuitry to achieve real-time monitoring of the temperature, input power, reflected power, and weight of the reaction unit, as well as control of the automatic protection unit.

[0039] Example 1 A design and application method for a microwave-driven catalytic reforming process for preparing petroleum products and gaseous hydrocarbons of polyolefin plastics. The microwave catalytic reforming process design diagram is shown below. Figure 1 As shown, it includes the following steps: (1) Select a single-port reaction tube with a side vent pipe as the inner reactor, and a reaction tube with a larger inner diameter than the outer diameter of the inner reactor as the outer reactor.

[0040] (2) First, add 5 g of polyethylene (PE) plastic to the inner reactor, followed by 6 g of ZSM-5 molecular sieve with a silica-alumina ratio of 21 (the molecular sieve occupies a space with an inner diameter of 30.0 mm and a height of 36.5 mm in the inner reactor). The plastic is kept in the lower layer, and the molecular sieve is kept in the upper layer, with a horizontal material contact surface between the two materials. The molecular sieve does not need to be supported and can sink freely under the action of gravity.

[0041] (3) Add 20 g of graphite to the external reactor. The height of the bed formed by the graphite stack is higher than the sum of the heights of the beds formed by plastic and molecular sieve.

[0042] (4) Connect all units of the microwave reaction device. The carrier gas component is nitrogen. Nitrogen enters through the inlet of the inner reactor and is transported downward from the top of the inner reactor. The gas flow rate is 100 mL / min. It is continuously introduced for 10 min before the reaction to ensure the stability of the gas environment inside the device.

[0043] (5) Start the power supply and control the input microwave power to 520 W (the highest temperature of the inner reactor is 450±50℃). Maintain the supply of nitrogen gas. The reaction time is 30 min. The catalytic reforming product is discharged from the gas outlet at the top of the inner reactor and cooled in the cold trap. The condensation temperature is controlled at -6 °C. The product components are detected by chromatography. During the cracking reaction, polyethylene is continuously consumed, and the catalyst continuously sinks under the action of gravity to maintain a horizontal material contact surface.

[0044] Analysis using gas chromatography-mass spectrometry (GC-MS) revealed a raw material conversion rate of 88%, with oil components comprising 53.4 wt% of the product. Aromatics exhibited a selectivity of 44.5 wt% in the total product, while BTEX (benzene, toluene, ethylbenzene, xylene) showed a selectivity of 40.3 wt% in the total product.

[0045] Example 2 A design and application method for a microwave-driven catalytic reforming process for preparing petroleum products and gaseous hydrocarbons of polyolefin plastics. The microwave catalytic reforming process design diagram is shown below. Figure 1 As shown, it includes the following steps: (1) Select a single-port reaction tube with a side vent pipe as the inner reactor, and a reaction tube with a larger inner diameter than the outer diameter of the inner reactor as the outer reactor.

[0046] (2) First, add 5 g of polyethylene (PE) plastic to the inner reactor, followed by 6 g of ZSM-5 molecular sieve with a silica-to-alumina ratio of 300 (the molecular sieve occupies a space with an inner diameter of 30.0 mm and a height of 36.5 mm in the inner reactor). The plastic is kept in the lower layer, and the molecular sieve is kept in the upper layer, with the two materials in interfacial contact. The molecular sieve does not require any support and can sink freely under gravity.

[0047] (3) Add 20 g of graphite to the external reactor. The height of the bed formed by the graphite stack is higher than the sum of the heights of the beds formed by plastic and molecular sieve.

[0048] (4) Connect all units of the microwave reaction device. The carrier gas component is nitrogen. Nitrogen enters through the inlet of the inner reactor and is transported downward from the top of the inner reactor. The gas flow rate is 100 mL / min. It is continuously introduced for 10 min before the reaction to ensure the stability of the gas environment inside the device.

[0049] (5) Start the power supply and control the input microwave power to 520 W (the inner reactor reaches a maximum of 450±50℃). The reaction time is 30 min. The catalytic reforming product is discharged from the gas outlet at the top of the inner reactor and cooled in the cold trap. The condensation temperature is controlled at -6 °C. The product components are detected by chromatography. During the cracking reaction, polyethylene is continuously consumed, and the catalyst continuously sinks under the action of gravity to maintain a horizontal material contact surface.

[0050] Analysis using gas chromatography-mass spectrometry (GC-MS) revealed a raw material conversion rate of 91%, an oil component content of 20.3 wt% in the product, and an olefin product selectivity of 49.2 wt% in the total product, with the sum of the selectivities of ethylene, propylene, and butene being 34.3 wt%.

[0051] Example 3 A design and application method for a microwave-driven catalytic reforming process for preparing petroleum products and gaseous hydrocarbons of polyolefin plastics. The microwave catalytic reforming process design diagram is shown below. Figure 1 As shown, it includes the following steps: (1) Select a single-port reaction tube with a side vent pipe as the inner reactor, and a reaction tube with a larger inner diameter than the outer diameter of the inner reactor as the outer reactor.

[0052] (2) First, add 5 g of polyethylene (PE) plastic to the inner reactor, followed by 6 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 21 and doped with 1 wt% Zr (the molecular sieve occupies a space with an inner diameter of 30.0 mm and a height of 36.5 mm in the inner reactor). The plastic is kept in the lower layer, and the molecular sieve is kept in the upper layer, with a horizontal material contact surface between the two materials. The molecular sieve does not need to be supported and can sink freely under the action of gravity.

[0053] (3) Add 20 g of graphite to the external reactor. The height of the bed formed by the graphite stack is higher than the sum of the heights of the beds formed by plastic and molecular sieve.

[0054] (4) Connect all units of the microwave reaction device. The carrier gas component is nitrogen. Nitrogen enters through the inlet of the inner reactor and is transported downward from the top of the inner reactor. The gas flow rate is 100 mL / min. It is continuously introduced for 10 min before the reaction to ensure the stability of the gas environment inside the device.

[0055] (5) Start the power supply and control the input microwave power to 520 W (the inner reactor reaches a maximum of 450±50℃). The reaction time is 30 min. The catalytic reforming product is discharged from the gas outlet at the top of the inner reactor and cooled in the cold trap. The condensation temperature is controlled at -6 °C. The product components are detected by chromatography. During the cracking reaction, polyethylene is continuously consumed, and the catalyst continuously sinks under the action of gravity to maintain a horizontal material contact surface.

[0056] Analysis using gas chromatography-mass spectrometry (GC-MS) revealed a raw material conversion rate of 92%, with oil components comprising 46.5 wt% of the product. The selectivity of olefin products in the total product was 36.3 wt%, and the selectivity of aromatic products in the total product was 30.6 wt%. Among these, BTEX (benzene, toluene, ethylbenzene, xylene) had a selectivity of 27.4 wt% in the total product.

[0057] Example 4 A design and application method for a microwave-driven catalytic reforming process for preparing petroleum products and gaseous hydrocarbons of polyolefin plastics. The microwave catalytic reforming process design diagram is shown below. Figure 1 As shown, it includes the following steps: (1) Select a single-port reaction tube with a side vent pipe as the inner reactor, and a reaction tube with a larger inner diameter than the outer diameter of the inner reactor as the outer reactor.

[0058] (2) First, add 5 g of polyethylene (PE) plastic to the inner reactor, followed by 6 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 300 and doped with 1 wt% Zr (the molecular sieve occupies a space with an inner diameter of 30.0 mm and a height of 36.5 mm in the inner reactor). The plastic is kept in the lower layer, and the molecular sieve is kept in the upper layer, with a horizontal material contact surface between the two materials. The molecular sieve does not need to be supported and can sink freely under the action of gravity.

[0059] (3) Add 20 g of graphite to the external reactor. The height of the bed formed by the graphite stack is higher than the sum of the heights of the beds formed by plastic and molecular sieve.

[0060] (4) Connect all units of the microwave reaction device. The carrier gas component is nitrogen. Nitrogen enters through the inlet of the inner reactor and is transported downward from the top of the inner reactor. The gas flow rate is 100 mL / min. It is continuously introduced for 10 min before the reaction to ensure the stability of the gas environment inside the device.

[0061] (5) Start the power supply and control the input microwave power to 520 W (the inner reactor reaches a maximum of 450±50℃). The reaction time is 30 min. The catalytic reforming product is discharged from the gas outlet at the top of the inner reactor and cooled in the cold trap. The condensation temperature is controlled at -6 °C. The product components are detected by chromatography. During the cracking reaction, polyethylene is continuously consumed, and the catalyst continuously sinks under the action of gravity to maintain a horizontal material contact surface.

[0062] Analysis using gas chromatography-mass spectrometry (GC-MS) revealed a raw material conversion rate of 95%. The selectivity of aromatic components in the total product was 20.5 wt%, the selectivity of BTEX (benzene, toluene, ethylbenzene, xylene) in the total product was 18.5 wt%, the selectivity of olefin products in the total product was 56.6 wt%, and the combined selectivity of ethylene, propylene, and butene in the total product was 45.6 wt%.

[0063] Example 5 A design and application method for a microwave-driven catalytic reforming process for preparing petroleum products and gaseous hydrocarbons of polyolefin plastics. The microwave catalytic reforming process design diagram is shown below. Figure 1 As shown, it includes the following steps: (1) Select a single-port reaction tube with a side vent pipe as the inner reactor, and a reaction tube with a larger inner diameter than the outer diameter of the inner reactor as the outer reactor.

[0064] (2) First, add 5 g of polyethylene (PE) plastic to the inner reactor, followed by 6 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 300 and doped with 1 wt% W (the molecular sieve occupies a space with an inner diameter of 30.0 mm and a height of 36.5 mm in the inner reactor). The plastic is kept in the lower layer, and the molecular sieve is kept in the upper layer, with a horizontal material contact surface between the two materials. The molecular sieve does not need to be supported and can sink freely under the action of gravity.

[0065] (3) Add 20 g of graphite to the external reactor. The height of the bed formed by the graphite stack is higher than the sum of the heights of the beds formed by plastic and molecular sieve.

[0066] (4) Connect all units of the microwave reaction device. The carrier gas component is nitrogen. Nitrogen enters through the inlet of the inner reactor and is transported downward from the top of the inner reactor. The gas flow rate is 100 mL / min. It is continuously introduced for 10 min before the reaction to ensure the stability of the gas environment inside the device.

[0067] (5) Start the power supply and control the input microwave power to 520 W (the inner reactor reaches a maximum of 450±50℃). The reaction time is 30 min. The catalytic reforming product is discharged from the gas outlet at the top of the inner reactor and cooled in the cold trap. The condensation temperature is controlled at -6℃. The product components are detected by chromatography. During the cracking reaction, polyethylene is continuously consumed, and the catalyst continuously sinks under the action of gravity to maintain a horizontal material contact surface.

[0068] Analysis using gas chromatography-mass spectrometry (GC-MS) revealed a raw material conversion rate of 95%. The selectivity of aromatic components in the total product was 19.1 wt%, the selectivity of BTEX (benzene, toluene, ethylbenzene, xylene) in the total product was 15.4 wt%, and the selectivity of olefin products in the total product was 51.2 wt%, with the sum of the selectivities of ethylene, propylene, and butene in the total product being 40.3 wt%.

[0069] Example 6 A design and application method for a microwave-driven catalytic reforming process for preparing petroleum products and gaseous hydrocarbons of polyolefin plastics. The microwave catalytic reforming process design diagram is shown below. Figure 1 As shown, it includes the following steps: (1) Select a single-port reaction tube with a side vent pipe as the inner reactor, and a reaction tube with a larger inner diameter than the outer diameter of the inner reactor as the outer reactor.

[0070] (2) First, add 5 g of polyethylene (PE) plastic to the inner reactor, followed by 6 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 300 and doped with 1 wt% Ni (the molecular sieve occupies a space with an inner diameter of 30.0 mm and a height of 36.5 mm in the inner reactor). The plastic is kept in the lower layer, and the molecular sieve is kept in the upper layer, with a horizontal material contact surface between the two materials. The molecular sieve does not need to be supported and can sink freely under the action of gravity.

[0071] (3) Add 20 g of graphite to the external reactor. The height of the bed formed by the graphite stack is higher than the sum of the heights of the beds formed by plastic and molecular sieve.

[0072] (4) Connect all units of the microwave reaction device. The carrier gas component is nitrogen. Nitrogen enters through the inlet of the inner reactor and is transported downward from the top of the inner reactor. The gas flow rate is 100 mL / min. It is continuously introduced for 10 min before the reaction to ensure the stability of the gas environment inside the device.

[0073] (5) Start the power supply and control the input microwave power to 520 W (the inner reactor reaches a maximum of 450±50℃). The reaction time is 30 min. The catalytic reforming product is discharged from the gas outlet at the top of the inner reactor and cooled in the cold trap. The condensation temperature is controlled at -6℃. The product components are detected by chromatography. During the cracking reaction, polyethylene is continuously consumed, and the catalyst continuously sinks under the action of gravity to maintain a horizontal material contact surface.

[0074] Analysis using gas chromatography-mass spectrometry (GC-MS) revealed a raw material conversion rate of 79%. The selectivity of aromatic components in the total product was 16.5 wt%, the selectivity of BTEX (benzene, toluene, ethylbenzene, xylene) was 13.7 wt%, and the selectivity of olefin products was 36.2 wt%, with ethylene, propylene, and butene having a selectivity of 30.2 wt%.

[0075] Example 7 A design and application method for a microwave-driven catalytic reforming process for preparing petroleum products and gaseous hydrocarbons of polyolefin plastics. The microwave catalytic reforming process design diagram is shown below. Figure 1 As shown, it includes the following steps: (1) Select a single-port reaction tube with a side vent pipe as the inner reactor, and a reaction tube with a larger inner diameter than the outer diameter of the inner reactor as the outer reactor.

[0076] (2) First, add 5 g of a mixed plastic containing low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) (HDPE:LDPE:PP = 14:17:18) to the inner reactor. Then, add 6 g of ZSM-5 molecular sieve with a silica-to-alumina ratio of 300 and doped with 1 wt% Zr (the molecular sieve occupies a space with an inner diameter of 30.0 mm and a height of 36.5 mm in the inner reactor). The plastic is kept in the lower layer, and the molecular sieve is kept in the upper layer, with a horizontal material contact surface between the two materials. The molecular sieve does not require any support and can sink freely under gravity.

[0077] (3) Add 20 g of graphite to the external reactor. The height of the bed formed by the graphite stack is higher than the sum of the heights of the beds formed by plastic and molecular sieve.

[0078] (4) Connect all units of the microwave reaction device. The carrier gas component is nitrogen. Nitrogen enters through the inlet of the inner reactor and is transported downward from the top of the inner reactor. The gas flow rate is 100 mL / min. It is continuously introduced for 10 min before the reaction to ensure the stability of the gas environment inside the device.

[0079] (5) Start the power supply and control the input microwave power to 520 W (the inner reactor reaches a maximum of 450±50℃). The reaction time is 30 min. The catalytic reforming product is discharged from the gas outlet at the top of the inner reactor and cooled in the cold trap. The condensation temperature is controlled at -6℃. The product components are detected by chromatography. During the cracking reaction, the raw materials are continuously consumed, and the catalyst continuously sinks under the action of gravity to maintain a horizontal material contact surface.

[0080] Analysis using gas chromatography-mass spectrometry (GC-MS) revealed a raw material conversion rate of 95%. The selectivity of aromatic components in the total product was 14.4 wt%, the selectivity of BTEX (benzene, toluene, ethylbenzene, xylene) in the total product was 11.0 wt%, and the selectivity of olefin products in the total product was 52.7 wt%, with the sum of the selectivities of ethylene, propylene, and butene in the total product being 40.2 wt%.

[0081] Example 8 A design and application method for a microwave-driven catalytic reforming process for preparing petroleum products and gaseous hydrocarbons of polyolefin plastics. The microwave catalytic reforming process design diagram is shown below. Figure 1 As shown, it includes the following steps: (1) Select a single-port reaction tube with a side vent pipe as the inner reactor, and a reaction tube with a larger inner diameter than the outer diameter of the inner reactor as the outer reactor.

[0082] (2) First, add 5 g of polyethylene (PE) plastic to the inner reactor, followed by 6 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 300 and doped with 1 wt% Zr (the molecular sieve occupies a space with an inner diameter of 23.0 mm and a height of 60.0 mm in the inner reactor). The plastic is kept in the lower layer, and the molecular sieve is kept in the upper layer, with a horizontal material contact surface between the two materials. The molecular sieve does not need to be supported and can sink freely under the action of gravity.

[0083] (3) Add 20 g of graphite to the external reactor. The height of the bed formed by the graphite stack is higher than the sum of the heights of the beds formed by plastic and molecular sieve.

[0084] (4) Connect all units of the microwave reaction device. The carrier gas component is nitrogen. Nitrogen enters through the inlet of the inner reactor and is transported downward from the top of the inner reactor. The gas flow rate is 100 mL / min. It is continuously introduced for 10 min before the reaction to ensure the stability of the gas environment inside the device.

[0085] (5) Start the power supply and control the input microwave power to 520 W (the inner reactor reaches a maximum of 450±50℃). The reaction time is 30 min. The catalytic reforming product is discharged from the gas outlet at the top of the inner reactor and cooled in the cold trap. The condensation temperature is controlled at -6 °C. The product components are detected by chromatography. During the cracking reaction, polyethylene is continuously consumed, and the catalyst continuously sinks under the action of gravity to maintain a horizontal material contact surface.

[0086] See temperament map Figure 2 Analysis using gas chromatography-mass spectrometry (GC-MS) revealed a raw material conversion rate of 94%. The selectivity of aromatic components in the total product was 20.0 wt%, the selectivity of BTEX (benzene, toluene, ethylbenzene, xylene) in the total product was 18.2 wt%, the selectivity of olefin products in the total product was 56.1 wt%, and the combined selectivity of ethylene, propylene, and butene in the total product was 44.2 wt%.

[0087] Comparative Example 1 A design and application method for a microwave-driven catalytic reforming process for preparing petroleum products and gaseous hydrocarbons of polyolefin plastics. The microwave catalytic reforming process design diagram is shown below. Figure 1 As shown, it includes the following steps: (1) Select a single-port reaction tube with a side vent pipe as the inner reactor, and a reaction tube with a larger inner diameter than the outer diameter of the inner reactor as the outer reactor.

[0088] (2) First, add 5 g of polyethylene (PE) plastic to the inner reactor, followed by 6 g of ZSM-5 molecular sieve with a silica-to-alumina ratio of 300 (the molecular sieve occupies a space with an inner diameter of 30.0 mm and a height of 36.5 mm in the inner reactor). The plastic is kept in the lower layer, and the molecular sieve is fixed in the upper layer by a partition. There is no interfacial contact between the plastic and the molecular sieve, and a gap is left between the plastic and the molecular sieve.

[0089] (3) Add 20 g of graphite to the external reactor. The height of the bed formed by the graphite stack is higher than the sum of the heights of the beds formed by plastic and molecular sieve.

[0090] (4) Connect all units of the microwave reaction device. The carrier gas component is nitrogen. Nitrogen enters through the inlet of the inner reactor and is transported downward from the top of the inner reactor. The gas flow rate is 100 mL / min. It is continuously introduced for 10 min before the reaction to ensure the stability of the gas environment inside the device.

[0091] (5) Start the power supply and control the input microwave power to 520 W (the inner reactor reaches a maximum of 450±50℃). The reaction time is 30 min. The product of catalytic reforming is discharged from the gas outlet at the top of the inner reactor and cooled in the cold trap. The condensation temperature is controlled to be -6℃. The product components are detected by chromatography.

[0092] Analysis using gas chromatography-mass spectrometry (GC-MS) revealed a raw material conversion rate of 10%, with all products being straight-chain olefins and alkanes. This phenomenon is attributed to the fact that the maximum temperature of 500°C reached by the internal reactor was insufficient to convert the plastic into a vapor state, allowing it to break through the air layer and enter the catalyst layer for cracking and reforming reactions. Furthermore, this temperature was also insufficient to directly crack the plastic into short-chain olefins and alkanes.

[0093] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A microwave-driven catalytic reforming process for polyolefins, characterized in that, A microwave reaction device with a PLC control unit, a carrier gas regulation unit, and a reaction unit is used for polyolefin cracking and reforming. The polyolefin feedstock is located at the bottom of the reaction unit, and the catalyst is stacked on it to form a catalyst bed. The bottom of the catalyst bed is in contact with the polyolefin feedstock to form a horizontal material contact surface. The process includes: Under microwave irradiation, polyolefin raw materials undergo a pyrolysis reaction at the material contact surface, generating primary pyrolysis products; As the polyolefin feedstock is consumed, the catalyst sinks under gravity and maintains the horizontal material contact surface; The primary cracking products pass through the catalyst bed from bottom to top, and are pyrolyzed stepwise into oil components and / or gaseous hydrocarbon components, thereby achieving catalytic reforming of polyolefin feedstocks.

2. The process method according to claim 1, characterized in that, The pyrolysis reaction is carried out at a temperature of 200-550℃.

3. The process method according to claim 1, characterized in that, The mass ratio of the polyolefin raw material to the catalyst is 1:0.4-2.5; Preferably, a microwave absorber is disposed in contact with the periphery of the reaction unit; Preferably, the total mass ratio of the polyolefin raw material and the catalyst to the microwave absorber is 1:0.1-10; Preferably, the height of the bed formed by the catalyst stack is 30-60 mm; the height of the bed formed by the microwave absorber stack is greater than the total height of the bed formed by the polyolefin raw material and the catalyst stack.

4. The process method according to claim 1, characterized in that, The polyolefin raw material is selected from one or more of polyethylene plastic, polypropylene plastic, polyvinyl chloride plastic, polyethylene terephthalate plastic, polyurethane plastic, polystyrene plastic, cellulose, hemicellulose, lignin, glucose, and starch; The catalyst is selected from one or more of the following: molecular sieves without or with metal elements: carbon fiber, graphite, graphene oxide, reduced graphene oxide, carbon nanotubes, biochar, calcium oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, zinc oxide, and manganese oxide. The microwave absorber is selected from one or more of the following: unloaded silicon carbide, carbon fiber, graphite, graphene oxide, reduced graphene oxide, carbon nanotubes, biochar, iron oxide, cobalt oxide, nickel oxide, zinc oxide, and manganese oxide.

5. The process method according to claim 4, characterized in that, The metallic element is selected from one or more of zirconium, nickel, tungsten, zinc, iron, cobalt, copper, molybdenum, platinum, palladium, silver, and gold; The biochar is derived from the pyrolysis products of rice husks, coconut shells, bamboo, corn cobs, corn stalks, wheat straw, rice straw, or rapeseed straw.

6. The process method according to claim 1, characterized in that, The microwave reactor also includes an automatic protection unit, which uses the linkage mechanism between the automatic protection unit and the PLC control unit to realize real-time online control of the input power of the microwave reactor. Preferably, the linkage mechanism involves using a PLC control unit to monitor the input power, reaction unit temperature, and reflected power in real time. When the reaction unit temperature reaches 200-550℃, the system automatically reduces the input power and maintains the reaction temperature. When the set reaction time is reached, the system automatically stops microwave heating. When the reflected power exceeds 50% of the input power, the protection unit is automatically activated to stop the microwave generator from working.

7. The process method according to claim 1, characterized in that, The microwave generator of the microwave reaction device is a magnetron or a solid-state source, and the operating mode is single-mode or multi-mode, with an operating frequency of 2.45 GHz or 915 MHz. The input power of the microwave reaction device is 0-8000 W.

8. The process method according to claim 1, characterized in that, An air inlet and an air outlet are respectively provided at the top of the reaction unit, and the air inlet and the air outlet do not interfere with each other; Preferably, the carrier gas regulating unit supplies carrier gas to the reaction unit through the gas outlet; Preferably, the carrier gas is selected from one or more of argon, nitrogen, and helium, and the carrier gas flow rate ranges from 20 to 250 mL / min.

9. The process method according to claim 1, characterized in that, The microwave reaction device is also equipped with Temperature monitoring unit is used to measure the real-time temperature of polyolefin raw materials and catalysts; A power detection unit is used to measure the input power and reflected power of the microwave reaction device; The cold trap liquefaction unit is used to reduce the temperature inside the microwave reaction device and to achieve the liquefaction and collection of reaction products.

10. The process method according to claim 1, characterized in that, The gaseous hydrocarbon component is selected from one or more of hydrogen, low-carbon hydrocarbons, and carbon monoxide; The oil components are selected from gasoline and diesel components, which are mainly composed of benzene series compounds.

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